Production of hydrogen peroxide

ABSTRACT

Hydrogen peroxide is produced by liquid phase molecular oxygen oxidation of methyl benzyl alcohol. Inhibiting impurities are removed prior to oxidation.

RELATED APPLICATIONS

This application is a continuation-in-part of copending application Ser.No. 07/295,409 filed Jan. 10, 1989, U.S. Pat. No. 4,897,252.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the production of hydrogen peroxide bythe oxidation of methyl benzyl alcohol.

2. Description of the Prior Art

Hydrogen peroxide is an important chemical of commerce which is producedin very large quantities for use in a number of industrial applications.The predominant process used commercially for the production of hydrogenperoxide involves the oxidation of anthrahydroquinone, extraction ofhydrogen peroxide and reduction of the resulting anthraquinone toanthrahydroquinone which is reused. This process requires very highcapital expenditures in that use of a working solvent with efficientrecycle of various process components is necessary.

Substantial efforts have been directed to processes which involve directcombination of hydrogen and oxygen but thus far such processes have notfound widespread success.

Hydrogen peroxide has been formed by the oxidation of secondaryalcohols. At one time the production of hydrogen peroxide by oxidationof isopropanol was practiced commercially. Other secondary alcoholswhich have been mentioned as possible starting materials for hydrogenperoxide production include methyl benzyl alcohol and cyclohexanol. See,for example, U.S. Pat. Nos. 2,871,102, 2,871,103, and 2,871,104 of ShellDevelopment.

Hydrogen peroxide has also been formed by oxidation of high boilingsecondary alcohols such as diaryl methanol, the product hydrogenperoxide being stripped from the reaction mixture during oxidation; seeU.S. Pat. No. 4,303,632.

In certain commercial technologies, substantial quantities of varioussecondary alcohols are produced. For example, in the coproduction ofpropylene oxide and styrene monomer by hydroperoxide epoxidation, methylbenzyl alcohol, which is also referred to as alpha phenyl ethanol,1-phenyl ethanol or methyl phenyl carbinol, is formed and ultimatelyconverted by dehydration to styrene monomer. See U.S. Pat. No.3,351,635.

The present invention provides a process where commercial streamscontaining methyl benzyl alcohol can be employed effectively andefficiently for hydrogen peroxide production.

SUMMARY OF THE INVENTION

In accordance with the invention, an improved process for the productionof hydrogen peroxide by oxidation of methyl benzyl alcohol is provided.In particular, the process of this invention involves the production ofhydrogen peroxide by molecular oxygen oxidation of methyl benzyl alcoholin the liquid phase wherein contaminating impurities which inhibit thehydrogen peroxide production are removed or are converted tonon-inhibiting materials prior to oxidation. Acetophenone is acoproduct.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying FIG. 1 illustrates in schematic form a suitableembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Commercially available sources of methyl benzyl alcohol, for example,methyl benzyl alcohol process streams which are produced in thecoproduction of propylene oxide and styrene monomer, containcontaminants which seriously interfere with oxidation to hydrogenperoxide. In accordance with the present invention, these contaminantsare removed or converted to non-inhibiting materials prior to oxidationand production of hydrogen peroxide.

In accordance with the present invention, methyl benzyl alcohol isoxidized in the liquid phase with molecular oxygen at elevatedtemperatures and pressure with the concentration of water in thereaction mixture maintained below 4% by weight, preferably below 2% byweight and most preferably below 1% by weight. In this way high reactionrates and selectivities to hydrogen peroxide can be achieved.

In an especially preferred embodiment of the invention, hydrogenperoxide production can be integrated with the production of propyleneoxide and styrene monomer by epoxidation with ethyl benzenehydroperoxide. In this embodiment, feed to the methyl benzyl alcoholoxidation comprises a methyl benzyl alcohol/acetophenone process streamfrom the propylene oxide and styrene monomer process as will behereinafter described.

The oxidant which is used in the present invention is molecular oxygen.It is a convenient source of the oxygen although pure oxygen,oxygen-enriched air, oxygen diluted with various inerts such as argon,carbon dioxide and the like can be used.

The conditions of temperature and pressure are such as to maintain thereaction mixture in the liquid phase. Elevated temperatures ranging fromabout 100°-250° C., preferably 120°-180° C., are employed to achievereasonable reaction rates.

It is important to provide substantial partial pressures of oxygensufficient to maintain reasonable reaction rates. A preferred range is15 to 250 psi partial pressure of oxygen in the feed gases, with abroader useful range being 0.5 to 1000 psi.

Total pressure in the reaction zone should be sufficient to maintain thereaction mixture in the liquid phase. Generally, pressures in the rangeof 5 psig to 1000 psig are useful.

Metal contaminants and other materials which promote peroxidedecomposition are to be avoided in the reaction zone. Known peroxidestabilizers such as pyrophosphates are useful and can be employed.

The oxidation of methyl benzyl alcohol to hydrogen peroxide andacetophenone is an exothermic reaction which requires removal of theheat of reaction. This can be accomplished, for example, by circulatinga portion of the reaction mixture through indirect cooling means.Alternatively, the heat can be removed by boil-up and condensation ofcomponents of the reaction mixture.

Essential to practice of the invention is the maintaining of low waterconcentrations in the liquid reaction mixture, i.e. water concentrationbelow 4 wt. %, preferably below 2 wt. % and most preferably below 1 wt.% water in the reaction mixture.

Water concentration can be controlled in a number of ways. In the firstinstance, the water content of the various feed materials isappropriately kept to a minimum. In batch or continuous systems, watercan be removed as a vapor from the reaction zone, for example, alongwith nitrogen, unreacted oxygen and various other components of thereaction mixture. Whereas in conventional systems this water iscondensed and refluxed to the reaction zone, in practice of the presentinvention the water removed as vapor is not returned to the reactionzone thus preventing build-up of substantial concentrations of water inthe reaction mixture. In conjunction with this procedures, or as analternative thereto, liquid reaction mixture can be removed, hydrogenperoxide and water can be separated therefrom and the remainingcomponents further processed or recycled.

The invention can be further described with reference to the attacheddrawing which illustrates in schematic form an especially preferredembodiment. Referring to the drawing, a process stream from a commercialprocess for propylene oxide/styrene monomer coproduction comprisedmainly of methyl benzyl alcohol, acetophenone and ethyl benzene in line101 is combined with a methyl benzyl alcohol stream in line 102 fromacetophenone hydrogenation and passed to distillation zone 103.

By conventional distillation ethyl benzene is separated overhead vialine 104 for recycle to the propylene oxide/styrene monomer process. Ahigher boiling stream mainly comprised of methyl benzyl alcohol andacetophenone and containing small amounts of phenol and ethyl phenols isseparated from distillation zone 103 through line 105.

A portion of the methyl benzyl alcohol and acetophenone stream passesvia lines 106, 110 and 111 to dehydration zone 112. The remainingportion of this stream passes via line 107 to purification zone 108.

It has been found in accordance with the present invention, that certaincompound such as phenol and ethyl phenols which are usually present withmethyl benzyl alcohol in commercial streams severely inhibit themolecular oxygen oxidation of methyl benzyl alcohol to hydrogen peroxideand acetophenone. Accordingly, the methyl benzyl alcohol andacetophenone stream from distillation zone 103 is first treated inpurification zone 108 to remove materials which inhibit methyl benzylalcohol oxidation or to convert these materials to non-inhibitivecompounds.

Preferably, purification zone 108 comprises both distillation andcaustic and/or ion exchange treatment. By distillation, ethyl phenolscan be separated as high boiling material from methyl benzyl alcohol andacetophenone. Basic ion exchange resins such as poly(vinylpyridine)resins can be employed to separate the phenols as described, forexample, in Sumitomo Japanese Patent Publication 39025 of 1981. Caustictreatment is effective to remove phenol.

From purification zone 108, the methyl benzyl alcohol/acetophenonestream passes via line 113 to oxidation zone 114 wherein the methylbenzyl alcohol is reacted with molecular oxygen to form hydrogenperoxide and acetophenone. As shown, the molecular oxygen is provided byair introduced via line 115.

Conditions of temperature and pressure are maintained in zone 114effective to maintain the reaction mixture in the liquid phase and tomaintain high reaction rate and selectivity to hydrogen peroxide andacetophenone. The water content of the reaction mixture is maintainedbelow 4 wt. %, preferably below 2 wt. % and most preferably below 1 wt.% by stripping water formed during the oxidation out of the reactionmixture with unreacted oxygen and inert gases via line 140.

Liquid reaction mixture which contains product hydrogen peroxide passesfrom 114 via line 116 and is processed for the recovery of the hydrogenperoxide. In an especially preferred practice as describe din detail incopending application Ser. No. 07/295,411, filed Jan. 10, 1989, ethylbenzene extraction is used in the separation of the oxidate mixture. Thedisclosure of said copending application is incorporated herein byreference.

The oxidate is admixed with ethyl benzene introduced via line 137 andwith an ethyl benzene extraction mixture from back extraction extractor124 via line 117. The mixture passes to tower extractor 119 and flowscountercurrent to water which is introduced via line 120.

The organic phase comprised of ethyl benzene, methyl benzyl alcohol andacetophenone passes via line 122 to distillation zone 128. The aqueoushydrogen peroxide phase passes via line 122 to extractor 124 whereinsmall amounts of contained methyl benzyl alcohol and acetophenone areextracted with ethyl benzene introduced via line 123. The organic phaseis removed via line 117 and recycled to admixture with oxidate fromreactor 114.

The aqueous hydrogen peroxide phase passes via line 125 to purificationzone 126 from which the final purified hydrogen peroxide is recoveredvia line 127.

In separation zone 128, ethyl benzene is separated overhead and can berecycled to admixture with oxidate form reactor 114 via lines 130 and137.

Advantageously, the methyl benzyl alcohol and acetophenone stream passesvia line 129 to integration with a commercial propylene oxide/styrenemonomer process, as shown. The methyl benzyl alcohol and acetophenonepass via line 129 and are admixed with a comparable stream fromseparation zone 103 via lines 105, 106 and 110 and passed to dehydrationzone 112 wherein methyl benzyl alcohol is dehydrated to styrene monomer.Dehydration effluent is transferred via line 131 to zone 132 whereinproduct styrene monomer is recovered and removed via line 133.

The remaining mixture of unconverted methyl benzyl alcohol andacetophenone is admixed with ethyl benzene introduced via line 137 andpassed via line 134 to zone 135 wherein acetophenone is hydrogenated tomethyl benzyl alcohol. The effluent stream from 135 is recycled via 102to separation zone 103 and thus re-integrated into the process.

The following examples illustrate the practice of the invention. Unlessotherwise stated, units are parts by weight per hour and percentages areweight percent.

EXAMPLE 1

Referring to the drawing, 1000 parts of a mixture comprised of 65% ethylbenzene, 29% methyl benzyl alcohol and 6% acetophenone in line 101 iscombined with 314.5 parts of a 52% ethyl benzene, 43% methyl benzylalcohol and 5% acetophenone stream from line 102 and passed todistillation zone 103. About 651 parts of ethyl benzene are recoveredoverhead and recycled via line 104 to the ethyl benzene oxidation of apropylene oxide/styrene monomer process.

The bottom stream comprised of approximately 84% methyl benzyl alcoholand 16% acetophenone and containing 1200 ppm phenol and 1600 ppm 2, 3and 4 ethyl-phenols is divided into two streams--90 parts passing vialines 106, 110 and 111 to dehydration zone 112 and 411 parts passing vialine 107 to purification zone 108.

In zone 108 the oxidation inhibiting phenols are separated bydistillation. Suitable conditions are an overhead pressure of 40 torr,overhead temperature of 116° C. and bottom temperature of 135° C. About205.5 parts of the bottoms, phenols-rich stream, comprised ofapproximately 84% methyl benzyl alcohol and 16% acetophenone andcontaining the predominance of the ethyl-phenols is sent via lines 109,110 and 111 to dehydration zone 112. About 205.5 parts of a phenols-leanstream, comprised of approximately 84% methyl benzyl alcohol and 16%acetophenone is sent via line 113 to oxidation reactor 114.

Conditions in the oxidation reactor are 140° C. and 300 psig; 66 partsof air are sparged into the reactor. Oxygen partial pressure in the ventgas exiting via line 140 is 16 psia. Methyl benzyl alcohol conversion inthe reactor is 30% with H₂ O₂ selectivity about 80%. About 217.5 partsof liquid reaction mixture comprised of 55.4% methyl benzyl alcohol,38.6% acetophenone, 5.3% H₂ O₂ and 0.7% H₂ O are removed via line 116,admixed with 178 parts pure ethyl benzene from line 137 and 56 parts ofan ethyl benzene recycle stream in line 117 from the ethyl benzene backextraction unit 124, comprised of 98.0% ethyl benzene, 1.7% methylbenzyl alcohol, 0.1% H₂ O and 0.2% acetophenone. The combined feed tothe H₂ O₂ extractor in line 118 is 448 parts, comprised of 51.5% ethylbenzene, 26.9% methyl benzyl alcohol, 18.7% acetophenone, 2.6% H₂ O₂ and0.3% H₂ O.

About 35 parts water is fed to the extractor via line 120. The heavieraqueous product from the extractor exits via line 122; it is about 45parts, comprised of approximately 25.6% H₂ O₂, 3% methyl benzyl alcoholand 0.5% acetophenone. The lighter organic product from the extractorexits via lines 121 to the ethyl benzene separation zone 128. Thisstream is about 438 parts, comprised of about 52.6% ethyl benzene, 27.5%methyl benzyl alcohol, 19.1% acetophenone, 0.7% H₂ O and 0.015% H₂ O₂.

The organics in the aqueous product from the H₂ O₂ extractor arerecovered by back extraction with ethyl benzene in extractor 124. About52.4 parts ethyl benzene are fed to 124 via line 123. The light organicproduct exits via line 117 and is sent back to be mixed with the organicfeed to the H₂ O₂ extractor 119. The heavy aqueous product exits vialine 125 and is sent to H₂ O₂ purification zone 126; it is about 43.4parts, comprised of 25.5% H₂ O₂ and 0.03% methyl benzyl alcohol and73.4% water.

Trace organics are separated in H₂ O₂ purification section 131, and theperoxide product is concentrated, if desired, by evaporation of water(not shown).

The organic product from the H₂ O₂ extractor is sent to ethyl benzeneseparation 128 via line 121. This stream is about 438 parts comprised of52.6% ethyl benzene, 27.5% methyl benzyl alcohol, 0.7% H₂ O and 19.1%acetophenone. The overhead ethyl benzene stream in amount of 230.6 partsis recovered in line 130 and recycled to H₂ O₂ extraction 119 and ethylbenzene back extraction 124. About 3.1 parts water is also removed (notshown) in Unit 128. The bottoms stream 129 is about 204.5 parts,comprised of 59% methyl benzyl alcohol and 41% acetophenone.

The combined streams in lines 110 and 129 in amount of 500 parts andcomprised of 74% methyl benzyl alcohol and 26% acetophenone isdehydrated in zone 112. About 95% conversion of methyl benzyl alcohol tostyrene occurs in 112, resulting in a product stream in line 131 of 500parts comprised of 4% methyl benzyl alcohol, 26% acetophenone, 60%styrene and 10% water. Styrene separation unit 132 separates 300 partsstyrene in line 133 and 51 parts water (not shown). The other productexits line 134 and is 149 parts, comprised of 12% methyl benzyl alcoholand 88% acetophenone. This is diluted with 163.5 parts ethyl benzene inline 137 and sent to acetophenone hydrogenation unit 135.

About 90% of the acetophenone fed to hydrogenation is converted byreaction with 2.1 parts hydrogen from line 136. The product stream inamount of 314.5 parts is recycled back to propylene oxide/styrenemonomer refining section 103 and is comprised of 52% ethyl benzene, 43%methyl benzyl alcohol and 5% acetophenone.

EXAMPLE 2

A synthetic feed stream corresponding to the composition of a typicalmethyl benzyl alcohol oxidation feed stream was prepared and treatedwith basic ion exchange resins to separate phenol impurities. The feedstream comprised about 47% methyl benzyl alcohol, 15% acetophenone, 34%ethyl benzene as well as 1000-14000 ppm phenol and phenol derivatives.The resins employed were poly(vinylpyridine) resin (Reillex 425 resinfrom Reilly Industries, Inc.) and strongly basic styrene divinyl benzenequaternary ammonium anion exchange resin (Amberlyst A-26 from Rohm andHaas). In the case of this latter resin, the copolymer waschloromethylated and then aminated with trimethyl amine; the functionalstructure is --N(CH₃)₃ ⁺ Cl⁻.

The feed stream was passed through a column packed with the resin at aflow rate of 0.3 to 1.5 gallons per minute per cubic foot of resin.Temperature was 20° to 40° C. The following table shows the resultsobtained.

                  TABLE 1                                                         ______________________________________                                                                    Flow Rate                                              Type of     Feed Phenols                                                                             gal/min/ft.sup.3                                                                       % Phenols                                Run  Resin       Content, ppm                                                                             of Resin removal                                  ______________________________________                                        1    Amberlyst A-26                                                                            1060       0.43     70.7                                     2    Reillex 425 1060       0.30     42.5                                     3    Reillex 425 1360       0.32     30.0                                     ______________________________________                                    

These results show that the resin treatment was effective in reducingthe phenols content. The Amberlyst resin was more effective for removingphenols. The treated methyl benzyl alcohol stream is oxidized withmolecular oxygen to form hydrogen peroxide as described in Example 1.

EXAMPLE 3

The synthetic oxidation feed from Example 2 was caustic treated toremove phenols. About 100 g of the feed were contacted at 32° C. with 20g 5% aqueous caustic, and the resulting mixture was separated intoaqueous and organic phases. Phenols removal from the organic stream was95%. The treated methyl benzyl alcohol stream is oxidized with molecularoxygen to form hydrogen eroxide as described in Example 1.

We claim:
 1. In a process for the production of hydrogen peroxide frommethyl benzyl alcohol contaminated with organic phenol impurities whichinhibit hydrogen peroxide formation, the improvement which comprisestreating the contaminated methyl benzyl alcohol to remove the saidphenol impurities or to convert the said phenol impurities tonon-inhibiting materials, and thereafter reacting the treated methylbenzyl alcohol with molecular oxygen to form hydrogen peroxide.
 2. Theprocess of claim 1 wherein the said organic phenol impurities areremoved from said methyl benzyl alcohol by distillation.
 3. The processof claim 1 wherein the said organic phenol impurities are removed fromsaid methyl benzyl alcohol by caustic treatment.
 4. The process of claim1 wherein the said organic phenol impurities and removed from saidmethyl benzyl alcohol by ion exchange resin treatment.
 5. The process ofclaim 1 wherein the said organic phenol impurities are removed from saidmethyl benzyl alcohol by distillation and caustic or ion exchange resintreatment.
 6. The process of claim 1 wherein said organic phenolimpurities are selected from the group consisting of phenol and ethylphenols.